Fix NPE in dependecy resolver when datasource is null

In some cases if you ask for resolving a dependency from the Neo store
data source when the latter is not available a NPE is thrown.  This
change will fix that behaviour by skipping the unavailable data source
from the list of possible dependency providers.

community/kernel/src/main/java/org/neo4j/kernel/impl/factory/PlatformModule.java

@@ -24,9 +24,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Supplier;
 
-import org.neo4j.graphdb.DependencyResolver;
 import org.neo4j.graphdb.factory.GraphDatabaseSettings;
 import org.neo4j.graphdb.security.URLAccessRule;
 import org.neo4j.helpers.collection.Iterables;
@@ -110,14 +108,10 @@ public PlatformModule( File providedStoreDir, Map<String, String> params, Databa
             GraphDatabaseFacadeFactory.Dependencies externalDependencies, GraphDatabaseFacade graphDatabaseFacade )
     {
         this.databaseInfo = databaseInfo;
-        dependencies = new org.neo4j.kernel.impl.util.Dependencies( new Supplier<DependencyResolver>()
-        {
-            @Override
-            public DependencyResolver get()
-            {
-                return dataSourceManager.getDataSource().getDependencyResolver();
-            }
-        } );
+        this.dataSourceManager = new DataSourceManager();
+        dependencies = new org.neo4j.kernel.impl.util.Dependencies(
+                new DataSourceManager.DependencyResolverSupplier( dataSourceManager ) );
+
         life = dependencies.satisfyDependency( createLife() );
         this.graphDatabaseFacade = dependencies.satisfyDependency( graphDatabaseFacade );
 
@@ -172,7 +166,7 @@ public DependencyResolver get()
         // this was the place of the XaDataSourceManager. NeoStoreXaDataSource is create further down than
         // (specifically) KernelExtensions, which creates an interesting out-of-order issue with #doAfterRecovery().
         // Anyways please fix this.
-        dataSourceManager = dependencies.satisfyDependency( new DataSourceManager() );
+        dependencies.satisfyDependency( dataSourceManager );
 
         availabilityGuard = new AvailabilityGuard( Clocks.systemClock(), logging.getInternalLog(
                 AvailabilityGuard.class ) );

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/state/DataSourceManager.java

@@ -21,6 +21,7 @@
 
 import java.util.function.Supplier;
 
+import org.neo4j.graphdb.DependencyResolver;
 import org.neo4j.helpers.Listeners;
 import org.neo4j.kernel.NeoStoreDataSource;
 import org.neo4j.kernel.api.KernelAPI;
@@ -131,4 +132,25 @@ public KernelAPI get()
     {
         return dataSource.getKernel();
     }
+
+    public static class DependencyResolverSupplier implements Supplier<DependencyResolver>
+    {
+        private DataSourceManager dataSourceManager;
+
+        public DependencyResolverSupplier( DataSourceManager dataSourceManager )
+        {
+            this.dataSourceManager = dataSourceManager;
+        }
+
+        @Override
+        public DependencyResolver get()
+        {
+            NeoStoreDataSource dataSource = dataSourceManager.getDataSource();
+            if ( dataSource == null )
+            {
+                return null;
+            }
+            return dataSource.getDependencyResolver();
+        }
+    }
 }

community/kernel/src/test/java/org/neo4j/kernel/impl/transaction/state/DependencyResolverSupplierTest.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2002-2016 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.kernel.impl.transaction.state;
+
+
+import org.junit.Test;
+
+import org.neo4j.graphdb.DependencyResolver;
+import org.neo4j.kernel.NeoStoreDataSource;
+import org.neo4j.kernel.impl.transaction.state.DataSourceManager.DependencyResolverSupplier;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class DependencyResolverSupplierTest
+{
+    @Test
+    public void shouldReturnTheDependencyResolveFromTheRegisteredDatasource() throws Exception
+    {
+        // given
+        DataSourceManager dataSourceManager = new DataSourceManager();
+        DependencyResolverSupplier supplier = new DependencyResolverSupplier( dataSourceManager );
+        NeoStoreDataSource neoStoreDataSource = mock( NeoStoreDataSource.class );
+        DependencyResolver dependencyResolver = mock( DependencyResolver.class );
+        when( neoStoreDataSource.getDependencyResolver() ).thenReturn( dependencyResolver );
+
+        // when
+        dataSourceManager.register( neoStoreDataSource );
+
+        // then
+        assertEquals( dependencyResolver, supplier.get() );
+    }
+
+    @Test
+    public void shouldReturnNullIfDataSourceHasBeenUnregistered() throws Exception
+    {
+        // given
+        DataSourceManager dataSourceManager = new DataSourceManager();
+        DependencyResolverSupplier supplier = new DependencyResolverSupplier( dataSourceManager );
+        NeoStoreDataSource neoStoreDataSource = mock( NeoStoreDataSource.class );
+        DependencyResolver dependencyResolver = mock( DependencyResolver.class );
+        when( neoStoreDataSource.getDependencyResolver() ).thenReturn( dependencyResolver );
+        dataSourceManager.register( neoStoreDataSource );
+
+        // when
+        dataSourceManager.unregister( neoStoreDataSource );
+
+        // then
+        assertEquals( null, supplier.get() );
+    }
+}

stresstests/src/test/java/org/neo4j/coreedge/stresstests/CatchUpLoad.java

@@ -36,6 +36,7 @@
 import org.neo4j.coreedge.discovery.EdgeClusterMember;
 import org.neo4j.coreedge.handlers.ExceptionMonitoringHandler;
 import org.neo4j.kernel.impl.transaction.log.TransactionIdStore;
+import org.neo4j.kernel.impl.util.UnsatisfiedDependencyException;
 import org.neo4j.kernel.internal.GraphDatabaseAPI;
 import org.neo4j.kernel.monitoring.Monitors;
 
@@ -150,7 +151,7 @@ private long txId( ClusterMember member, boolean fail )
             return database.getDependencyResolver().resolveDependency( TransactionIdStore.class )
                     .getLastClosedTransactionId();
         }
-        catch ( IllegalStateException ex )
+        catch ( IllegalStateException | UnsatisfiedDependencyException ex )
         {
             return errorValueOrThrow( !isStoreClosed( ex ) || fail, ex );
         }
@@ -168,8 +169,18 @@ private long errorValueOrThrow( boolean fail, RuntimeException error )
         }
     }
 
-    private boolean isStoreClosed( IllegalStateException ex )
+    private boolean isStoreClosed( RuntimeException ex )
     {
+        if ( ex instanceof UnsatisfiedDependencyException )
+        {
+            return true;
+        }
+
+        if ( !(ex instanceof IllegalStateException) )
+        {
+            return false;
+        }
+
         String message = ex.getMessage();
         return message.startsWith( "MetaDataStore for file " ) && message.endsWith( " is closed" );
     }